When storing and shipping filled bags, such as dog food bags, it is necessary that the bag be sealed so that grease, powders, and the like do not leak out during storage and shipment. A primary closure of this type is normally destroyed by the user when the bag is first opened. If the bag is to be resealable, it is also necessary to have a reusable secondary closure at the bag mouth, such as a zipper or a plastic zip-lock. Thus, two closure structures are incorporated at the mouth of the bag.
Examples of such structures will be found in Ferrell U.S. Pat. No. 4,241,865 and Sullivan U.S. Pat. No. 4,620,320, both using an inner chain stitch and an outer zipper; Griesbach U.S. Pat. No. 4,782,951, using a zip-lock outside sealed plastic sheets; and Provost U.S. Pat. No. 4,824,261, using an inner hook and loop fastener system (Velcro) inside an adhesively secured flap. In each of these systems two closure structures are required, adding to the cost of the package. Beck U.S. Pat. No. 4,498,192 uses flush cut tubes, in contrast to the present step cut.
In our bag closure system only one closure structure is needed to effect both the primary tight closure and the secondary resealable closure.